1. Field of the Invention
This invention is concerned with a process for the selective hydrogenation and simultaneous isomerization of a hydrocarbon feed stream containing a mixture of hydrocarbons of varying degrees of unsaturation and having 4 or more carbon atoms therein. The process comprises contacting the hydrocarbon feed stream with hydrogen gas under hydrogenating and isomerizing conditions in the presence of a suitable catalyst in a multi-stage packed bed catalytic reactor.
2. The Related Art
The selective hydrogenation and isomerization of hydrocarbon mixtures containing hydrocarbons with olefinic unsaturation is well-known in the art.
U.S. Pat. No. 3,485,887 is directed to the hydrogenation of C.sub.4 -hydrocarbon fractions containing n-butene-1 and butadiene by passing such into contact with a hydrogenation catalyst which is a metal of the Group V-VIII of the Periodic System in the presence of a hydrogen atmosphere. The product which is produced is stated to be high in n-butene and poor in butadiene content. The Patent states that the improvement of simultaneously isomerizing n-butene-1 in the fractions and produced in the hydrogenation to n-butene-2, comprises passing the C.sub.4 -hydrocarbon mixture in the liquid state downwardly over a fixed bed hydrogenation catalyst in a hydrogen atmosphere at an inlet temperature of the C.sub.4 -hydrocarbon mixture of about 10.degree.to 35.degree. C. and at an outlet temperature of the hydrogenated and isomerized product of 60.degree. to 90.degree. C.
U.S. Pat. No. 3,764,633 relates to a process and catalyst for isomerizing olefinic hydrocarbons while simultaneously hydrogenating polyolefinic hydrocarbons. Specifically, the Patent describes a process for the catalytic isomerization of monoolefinic hydrocarbons having a terminally-positioned double bond, the hydrocarbons containing at least four carbon atoms and being contained in a feedstream. The process comprises contacting a catalyst active for the isomerization of monoolefinic hydrocarbons with carbon monoxide to substantially deactivate the catalysts. The deactivated catalyst is then contacted with hydrogen to activate the catalyst for monoolefinic hydrocarbon isomerization. The activated catalyst is then contacted with a feedstream comprising the monoolefinic hydrocarbons to isomerize the same.
In column 4, line 68 through column 5, line 2 of this Patent, it is stated that the process may be carried out while introducing hydrogen into the reaction at a plurality of points within the reaction zone. Also, in column 7, lines 55 to 64 of the Patent, it is stated that distribution of the hydrogen introduced to the plurality of injection points will vary with the nature of the feedstock and the configuration of the bed. Generally, this Patent states that if two beds are employed, from about 95 to about 75 percent of the total hydrogen introduced will be added to the first bed, the remainder being added to the second bed. If more than two beds are employed, the addition of hydrogen will be in decreasing amounts to successive beds (column 7, lines 56-64).
U.S. Pat. No. 4,132,745 relates to a process for isomerizing 1-butene to 2-butene by contacting the 1-butene at a temperature from 50.degree. to 140.degree. C., in the presence of hydrogen, with an isomerization catalyst containing a Noble metal from Group VIII of the Periodic Classification of Elements. The catalyst is pretreated by contacting with a sulfur compound and then with hydrogen. The Patent states that the process described therein provides for the isomerization of 1-butene at a lower temperature than the prior processes and, accordingly, results in a more complete conversion to 2-butene.
U.S. Pat. No. 4,260,840 concerns selectively hydrogenating butadiene to butene in a C.sub.4 fraction containing at least 30 weight percent butene-1. Specifically, it is stated that a butene stream can be hydrogenated that contains a substantial amount of butene-1 of at least 30 percent and contains butadiene as an impurity, and which may contain other impurities. Such stream is hydrogenated by treatment with hydrogen under controlled conditions to convert the butadiene to butene while minimizing losses of butene-1 due to isomerization of butene-1 to butene-2 and hydrogenation of butene-1 and butene-2 to butane.
U.S. Pat. No. 4,312,741 describes a process for the catalytic hydrogenation of a hydrocarbon feedstock. The apparatus comprises a reactor unit having fluidized catalyst beds in a plurality of hydrogen inlet distribution fixtures. The separate beds may be contained within a single vessel or in separate vessels. The disclosure of this Patent does not allege the utility of the invention with respect to hydrogenating dienes or to isomerization, rather general utility for hydrogenation conversion reactions is alleged (column 1, lines 5-22 and column 5, lines 1-23). The multiplicity of fluidized beds is intended to improve catalyst mobility (column 2, lines 18-34).
U.S. Pat. No. 4,960,960 discloses a hydrogenation process utilizing first and second hydrogenation zones, wherein each may include two or more beds of catalyst, and each of which may be supplied with a hydrogen-containing feed gas (column 2, lines 43 through column 3, line 18; column 5, lines 18-25 and lines 45-48). The process described is not specific to any particular hydrogenation reaction (column 3, line 48 to column 5, line 17).
U.S. Pat. No. 4,469,907 is directed to a method of selectively hydrogenating highly unsaturated hydrocarbons by contacting a mixture of hydrocarbons of low unsaturated degree having four or more carbon atoms containing the highly unsaturated hydrocarbons into contact with hydrogen. The hydrogenation is conducted in the presence of a catalyst using a fixed bed reaction vessel. The process comprises supplying the hydrogen gas in a state of plural splits along the flow direction of the fixed bed reaction vessel. Also, the Patent states that the rate of flow of hydrogen gas in the second split or later split or splits along the flow direction of the fixed bed reaction vessel is 5 to 100% of the previous split (column 2, lines 43 to 48).
The Patent further states that the advantage of the invention therein is that a method is provided of selectably hydrogenating highly unsaturated hydrocarbons only, without being accompanied by isomerization of olefins (column 3, lines 46 to 51).